Hydraulic lifting systems are widely used in a range of areas and applications. One such application is offshore drilling where a hydraulic lifting or hoisting system can be used to lift drilling equipment. In such cases, the lifting system will need to carry very high loads, including both the drilling equipment (such as a top drive) and typically several hundred (or even thousand) meters of drill string extending towards the seafloor. Operational requirements also require that the lifting system be available for certain procedures in the case of an emergency, for example, to lift the drill string out of the BOP stack for an emergency disconnect.
High demands for reliability and availability therefore exist for such systems since the consequences (e.g., a well blow-out) in case of failures in such emergency situations can be extreme. A need therefore exists for systems and methods which further improve the reliability for hydraulic lifting systems used in offshore drilling and other applications.